main, nav {
    box-sizing: border-box;
    display: block;
}
main {
    width: 980px;
    height: auto;
    margin:0 auto;
}
main h4 {
    text-align: center;
}
.tabsbox {
    width: 100%;
    height: 400px;
    border: 1px solid #000;
}
.firstnav {
    display: flex;
    align-items: center;
    justify-content: space-between;
    border-bottom: 1px solid #888;
}
.firstnav ul {
    padding: 0;
    margin: 0;
    overflow: hidden;
}
.firstnav ul li {
    list-style-type: none;
    float: left;
    padding: 8px 20px;
    position: relative;
    border-right: 1px solid #888;
    cursor: pointer;
}
.firstnav ul li.liactive {
    color: red;
    background-color: pink;
    border-right: 0;
}
.close-carset {
    position: absolute;
    top:0;
    right:0;
    font-size: 10px;
    background-color: #000;
    color:#fff;
    padding: 0 5px;
    border-bottom-left-radius: 70%;
}
.tabadd {
    padding: 0 5px;
}
.tabadd span {
    font-size: 12px;
    padding: 0 3px;
    border: 1px solid #888;
    cursor: pointer;
}

.tabscon {
    width: 100%;
    height: auto;
}
.tabscon section {
    width: 100%;
    height: 100px;
    display: none;
    padding: 10px;
}
.tabscon section.conactive {
    display: block;
}